1. Field of the Invention
This invention generally relates to methods for adjusting the brightness and contrast of video displays to obtain repeatable image quality. More specifically, the invention relates to procedures for calibrating a video display to obtain a known or desired light level in response to an input level. In particular the invention relates to a calibration procedure in which electronics for driving a raster-scan display is shared with electronics for measuring the light output level. Calibration is useful where pictoral data should be consistently displayed for evaluation or analysis, as is the case with stimuli for visual and psychological testing or X-ray, CAT or ultrasonic scanner pictures.
2. Description of the Prior Art
(Prior Art Statement Under Rule 97)
Traditional approaches to calibrating raster-scan displays have involved external or internal photometers of varying degrees of complexity. But the photometers have operated independently of the electronics that generate the display test pattern. Photometers have, however, been built into the same housing as the display electronics. Typically the analog output of the photometer is converted to digital form and displayed numerically, with high precision requiring several digits of resolution. It is known that tests of vision must be conducted with calibrated video displays since clinically important differences in vision may be revealed by very small differences in display contrast.